The present invention relates to semiconductor packages used for various kinds of electric and electronic devices and a method for manufacturing the same and more particularly to a semiconductor package that is the same size as a semiconductor chip and is excellent in heat dissipation and a method for manufacturing the same.
In recent years, integration of semiconductor chips has become denser, and the functions of semiconductor chips have become ever more advanced. Consequently, the size of semiconductor chips and the number of electrodes on the semiconductor chip have become remarkable. On the other hand, it is required for a semiconductor package to be miniaturized to meet the demand for highly efficient and miniaturized electronic devices. Under these circumstances, a semiconductor package has shifted from the QFP (Quad Flat Package) type that is a semiconductor package having leads that are arranged around the peripheral part of the package to the BGA (Ball Grid Array) type that is a semiconductor package having electrodes arranged in area array on a bottom surface and the CSP (Chip Scale Package) type that is a semiconductor package that is further miniaturized.
FIG. 10 is a cross-sectional view showing the configuration of the CSP type semiconductor package. As shown in FIG. 10, bumps 102 are formed on electrodes formed on a semiconductor chip 101, the semiconductor chip 101 having connected to electrodes 104 formed on a wiring substrate 105 with face down via conductive resin 103. Further, sealing resin 107 is filled between the semiconductor chip 101 and the wiring substrate 105 to ensure the air-tightness. In FIG. 10, numeral 106 indicates an external lead electrode.
When the CSP type semiconductor package is used, an area of a circuit board can be utilized efficiently by miniaturizing the package. Thereby the package can be suitable for high speed and low noise circuits.
However, the above-mentioned conventional CSP type semiconductor package has the following problems. That is, when reliability such as thermal shock is evaluated, a sealing part between a semiconductor chip and a wiring substrate is prone to the cracking, because the thermal expansion coefficient of the semiconductor chip and that of the wiring substrate are different, and as a result, the air-tightness might deteriorate. Further, the cost and the number of steps of manufacturing may be increased by performing a process for sealing resin and coating. Further, the thermal conductivity between the semiconductor chip and the wiring substrate is very poor and it is very difficult for heat that is generated in the semiconductor chip to be released.
The present invention aims to solve the above-mentioned subjects and provide a semiconductor package which is not required to be sealed by resin, is excellent in reliability, air-tightness and thermal conductivity, and can be manufactured at low cost easily, and a method of manufacturing the same.
To accomplish the above-mentioned object, a first configuration of a semiconductor package according to the present invention comprises a semiconductor chip, a thermal conductive mixture including at least 70-95 weight parts of inorganic filler and 5-30 weight parts of thermosetting resin composition that is bonded to an electrode surface of the semiconductor chip where electrodes are formed and to edge surfaces of the semiconductor chip that adjoin the electrode surfaces, and an external lead electrode that is formed on the thermal conductive mixture and is electrically connected with the semiconductor chip.
According to a first configuration of the semiconductor package, it is not required to provide a further resin seal for a semiconductor chip using a thermal conductive mixture as a substrate and a semiconductor package excellent in thermal conductivity can be realized. Further, the thermal expansion coefficient of a thermal conductive mixture as a substrate in the in-plane direction is almost the same as that of a semiconductor chip. Therefore even after a reflow test is conducted, an abnormality in the interface of the semiconductor chip and the package is not observed particularly, and the electrical resistance value of the semiconductor package including a part connecting the semiconductor chip and an external lead electrode changes only very slightly. As a result, a semiconductor package excellent in reliability can be realized.
In a first configuration of the semiconductor package, it is preferable that a through-hole is formed in a thermal conductive mixture opposing to an electrode formed on a semiconductor chip.
Further, in this case, it is preferable that a conductive resin composition is filled in a through-hole and an external lead electrode is connected electrically with a semiconductor chip via the conductive resin composition. In this case, it is preferable that a conductive resin composition includes at least thermosetting resin, a curing agent and at least one kind of metallic powder selected from a group consisting of gold, silver, copper, palladium and nickel.
In a first configuration of the semiconductor package, it is preferable that a bump is formed on an electrode formed on a semiconductor chip. According to this preferable example, reliability-in electrically connecting the semiconductor chip with an external lead electrode can be improved. Further, in this case, it is preferable that the bump penetrates into a thermal conductive mixture and is integrated with the external lead electrode.
In a first configuration of the semiconductor package, it is preferable that the inorganic filler includes at least one selected from a group consisting of Al2O3, MgO, BN and AlN. This is because they have high thermal conductivity.
In a first configuration of the semiconductor package, it is preferable that the inorganic filler has a particle diameter in a range between 0.1-100 xcexcm.
In a first configuration of the semiconductor package, it is preferable that a thermosetting resin composition includes at least one kind of resin as a main component selected from a group consisting of epoxy resin, phenol resin and cyanate resin. This is because they are excellent in electric property and in mechanical property.
In a first configuration of the semiconductor package, it is preferable that a thermosetting resin composition includes brominated multi-functional epoxy resin as a main component and further includes novolak resin of bisphenol A as a curing agent and imidazole as a curing promoter.
In a first configuration of the semiconductor package, it is preferable that a thermal conductive mixture includes at least one kind selected from a group consisting of a coupling agent, a dispersing agent, a coloring agent and a mold-releasing agent.
To accomplish the above-mentioned object, a second configuration of a semiconductor package according to the present invention comprises a semiconductor chip, a thermal conductive mixture including at least 70-95 weight parts of inorganic filler and 5-30 weight parts of thermosetting resin composition that is bonded to an electrode surface of the semiconductor chip where electrodes are formed and to edge surfaces of the semiconductor chip that adjoin the electrode surface, and a wiring substrate having electrodes formed on both surfaces that is bonded to the thermal conductive mixture, and the electrodes formed on one surface of the wiring substrate are electrically connected with the semiconductor chip and the electrodes formed on another surface serve as an external electrode.
According to the second configuration of the semiconductor package, the spacing and the arrangement of the external lead electrodes can be changed by providing a wiring substrate and it becomes easy for a semiconductor package to be mounted on electronic devices.
In a second configuration of the semiconductor package, it is preferable that a main component of a wiring substrate is the same as that of a thermal conductive mixture. According to this preferable example, the thermal expansion coefficient of a peripheral part of a semiconductor becomes almost the same as that of an external lead electrode, and therefore reliability can be improved.
To accomplish the above-mentioned object, one configuration of a method for manufacturing a semiconductor package in the present invention comprises a step of overlapping a semiconductor chip on the thermal conductive sheet including at least 70-95 weight parts of inorganic filler and 5-30 weight parts of thermosetting resin composition and having flexibility in an uncured state with face down, a step of compressing the semiconductor chip and the thermal conductive sheet while being heated to bond the thermal conductive sheet to an electrode surface of the semiconductor chip where electrodes are formed and to edge surfaces of the semiconductor chip that adjoin the electrode surfaces, the thermosetting resin being cured to connect electrically an electrode formed on the semiconductor chip with an external lead electrode.
According to the method for manufacturing a semiconductor package in the present invention, a thermal conductive semiconductor package having a semiconductor chip that is mounted inside can be realized easily. This is because the thermal conductive sheet has flexibility in an uncured state, and therefore the thermal conductive sheet can be formed in a desirable shape at low temperature and at low pressure, and that a thermosetting resin composition contained in the thermal conductive sheet can be cured with pressure while being heated, and therefore a rigid substrate can be formed of the thermal conductive sheet.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that the temperature in a process for heat-pressing is in a range between 170-260xc2x0 C. This is because when the temperature is too low, a thermosetting resin composition is not cured sufficiently, and when the temperature is too high, the thermosetting resin composition starts to decompose.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that the pressure in a process for heat-pressing is in a range between 1-20 MPa. This is because when the pressure is too low, it becomes difficult for a thermal conductive sheet to be bonded to an electrode surface of a semiconductor chip where electrodes are formed and to edge surfaces of the semiconductor chip that adjoin the electrode surface, and when the pressure is too high, a semiconductor chip is prone to the damage.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that prior to a step of overlapping a semiconductor chip on a thermal conductive sheet with face down, a step of forming a through-hole in the thermal conductive sheet opposing to an electrode formed on the semiconductor chip is further included. According to this preferable example, when a bump is formed on an electrode formed in a semiconductor chip, it becomes easier to match a position of the semiconductor chip with that of the thermal conductive sheet. Further, in this case, it is preferable that a through-hole is formed by laser processing, drilling or punching. Further, in this case, it is preferable that after a through-hole is formed, a step of filling a thermosetting resin composition in the through-hole is further included. In this case, it is preferable that in a process for filling a conductive resin composition in a through-hole, the conductive resin composition is filled in only one part of the through-hole facing an opening and is not filled in another part of the through-hole facing another side. According to this preferable example, in integrating a semiconductor chip with a thermal conductive sheet, short circuit and disconnection caused by flowing out of excess conductive resin composition can be prevented. Further, as there is an opening at one side of the penetration, in overlapping a semiconductor chip having a bump formed on an electrode on a thermal conductive sheet, though there is a conductive resin composition, it becomes easier to match a position of the semiconductor chip with that of the thermal conductive sheet. In this case, it is preferable that a thermosetting resin composition includes at least one kind of metallic powder selected from a group consisting of gold, silver, copper, palladium and nickel, thermosetting resin and a curing agent.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that after a plurality of semiconductor chips are overlapped on a thermal conductive sheet with face down and the plurality of semiconductor chips and external lead electrodes are formed integrally, the plurality of semiconductor chips, the thermal conductive sheet and the external lead electrodes that are formed integrally are divided into individual semiconductor packages. According to this preferable example, many semiconductor packages can be obtained with one operation.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that after a bump is formed on an electrode formed on a semiconductor chip, the semiconductor chip is overlapped on a thermal conductive sheet with face down. Further, in this case, it is preferable that a bump is penetrated into a thermal conductive sheet to connect with an external lead electrode.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that after metallic foil is overlapped on a surface of a thermal conductive sheet that is opposite to a surface on which a semiconductor chip is overlapped and integrated, the metallic foil is patterned in a desirable shape to form an external lead electrode.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that an electrode pattern that is patterned in a desirable shape is transferred to a surface of a thermal conductive sheet at a side opposite to the surface on which a semiconductor chip is overlapped to form an external lead electrode.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that a wiring substrate whose surface is patterned in a desirable electrode shape is bonded to a surface of a thermal conductive sheet at a side opposite to the surface on which a semiconductor chip is overlapped is integrated with the thermal conductive sheet to form an external lead electrode.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that the inorganic filler includes at least one selected from a group consisting of Al2O3, MgO, BN and AlN.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that the inorganic filler has a particle diameter in a range between 0.1-100 xcexcm.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that a thermosetting resin composition includes at least one kind of resin as a main component selected from a group consisting of epoxy resin, phenol resin and cyanate resin.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that a thermosetting resin composition includes brominated multi-functional epoxy resin as a main component and further includes novolak resin of bisphenol A as a curing agent and imidazole as a curing promoter.
In the method for manufacturing a semiconductor package in the present invention, it is preferable that a thermal conductive sheet includes at least one kind selected from a group consisting of a coupling agent, a dispersing agent, a coloring agent and a mold-releasing agent.